The present invention relates to an inverting deflector device for strips of sheet material.
In particular, the present invention relates to a deflector and inverter device which can be used when it is necessary to deflect the direction of movement of a strip of sheet material by 90.degree., and when it is necessary to control the said strip in such a way that, after having been deflected, it is either the right way up or inverted.
The device forming the subject of the present invention, although usable with any type of flexible sheet material, can be used in a particularly advantageous way to deflect and, possibly, invert strips of paper advancing through a rotary printing press.
For simplicity and clarity, the following discussion will refer, without any loss of generality, to the particular mode of use specified above.
On rotary printing presses it is known to use, for each strip of printed paper supplied, for example, to the folding units, a deflector and inverter device normally constituted by a frame provided with bars, hereinafter indicated with the term "deflector bars", which form angles of 45.degree. with the input direction of the associated strip. By turning the input strip over the previously mentioned deflector bars it is possible to deflect the strip itself by 90.degree. to the right or to the left. Obviously, such a deflection automatically involves an inversion of the strip inasmuch as the surface which, at the input, faces, for example, upwardly, is on the other hand facing downwardly after the deflection.
For the purpose of avoiding the said inversion, in the cases where such is desired, the known deflector and inverter devices are provided laterally of the said deflector bars, and on opposite sides of these, with inverter rolls the function of which is immediately clear if one takes into consideration a practical case. If it is desired, for example, to deflect a strip of paper by 90.degree. in such a way that it shall not be inverted at the output, the strip itself is first passed over one of the previously mentioned inverter rolls and then onto the deflector bar which deflects it towards the right.
The use of the above described known deflector devices involves numerous disadvantages the main one of which is constituted by the friction which develops at the contact between the strips and the said deflector bar. Such friction is normally reduced by providing a plurality of holes on the bars for compressed air operable to form an air cushion under the strips. However, given the extent of the surface contact between the strips and the associated deflector bars it is necessary to adopt supply systems for the compressed air which are complicated and relatively costly in themselves.
Another disadvantage derives from the use of the said inverter rolls which, if used, extend the path of the strips of paper causing problems when the inverted strips must be combined with non-inverted strips.